1. Field of the Invention
The present invention relates to pumps for pumping fluids such as blood that are sensitive to mechanical forces or shear stress. More particularly, the present invention is a low profile pump inlet for use with a blood pump which may be implanted into a patient.
2. Description of Related Art
Many pumps are known in the art for pumping fluids in a wide range of applications. The basic function of such pumps is to either move a fluid from one point to another, or to impart energy to the fluid, raising it from one energy level to another. Recently, pumps have begun to be developed for use with sensitive fluids such as blood. Such pumps present very specific design requirements in order to function properly. Specifically, if a blood pump is intended to be used to support or assist the blood flow of a human patient, it must operate to move and raise the energy level of a blood flow without causing undue damage to the blood. Further, such pumps must operate without giving rise to illness in the patient. This is true whether the pump is intended for external use or for implantation.
Much research is currently in progress to develop implantable blood pumps such as ventricular assist devices (or “VADs”) and heart-replacement devices for use in a human patient for both short- and long-term use. When such pumps are intended for use in human patients, they face unique design challenges, including size and shape restraints, durability requirements, specific blood flow characteristics, and energy consumption restraints. These design challenges often dictate the usability of a potential pump in that they determine whether or not the pump will function sufficiently to sustain life without causing injury to the patient.
It is desirable to limit the size of an implantable pump in order to assure that it may be implanted in a patient without causing undue impingement on the patient's organs. Further, the implanted pump must be safely supported inside the patient, thus further restricting the size of the pump. Additionally, it is desirable to use a pump assembly that is durable, and which may last for a period of years. Yet further, an implantable blood pump needs to provide an even outflow of blood with a substantially smooth flow pattern in order to avoid stagnation or recirculation within the pump. Such improper flows diminish the efficiency of the pump, and may cause thrombosis or hemolysis, which could cause injury to a patient. Finally, a pump should be efficient in its energy consumption in order to prolong its periods of operability without requiring user intervention.
Many of these design considerations are influenced by the inlet used to carry the blood to be pumped into an internal chamber of the implantable pump. Such inlets may be relatively large in size, thus occupying a large volume, and contributing significantly to the weight of the complete pump apparatus. In addition, the inlets may simply carry a fluid without acting on the flow patterns of the blood passing through them. Turbulent flow patterns may exist in a blood flow due to bends and turns in the inflow conduit used to supply blood to the pump. Such curves may be required for proper installation and placement of the device in a specific patient. These design constraints could result in an uneven distribution of blood into the pump or thrombus formation. These conditions may cause inefficiency in the operation of the pump, or danger to the patient. Such inefficiency may affect the fluid circulating performance of the pump as well as the energy consumption characteristics of the pump.
Accordingly, it would be an advantage to provide a pump inlet for use with an implantable blood pump that had a low profile. It would be a further improvement to provide a pump inlet that at least partially suppresses undesirable flow patterns resulting from upstream bends and turns in a flow path, thus providing a substantially smooth outflow into the pump having a relatively uniform velocity profile. It would also be an improvement in the art to provide a pump inlet that distributes an outflow of blood substantially evenly about the impeller of a pump to promote the efficient operation of the implantable blood pump.
Such an apparatus is disclosed herein.